Compressors for refrigeration systems

ABSTRACT

A compressor for a sealed refrigeration system has a reciprocating piston operated by a drive shaft with an inclined end portion connected to the piston for example via a crank and slotted link. A non-rotatable coupling sleeve is fitted on the inclined end of the drive shaft and sealingly connected to a deformable diaphragm surrounding the shaft and hermetically sealing the bearing for the shaft from the interior of the compressor.

ilniie Pellizzeiti Paie [ 3,650,07 Apr. I, 11972 [54] COMPRESSURS FOIR REFRIGERATION SYSTEMS [72] Inventor: Italo Pellizzetti, Corso Massimo DAzeglio l0, Turin, Italy 22 Filed: July 17, 1970 21 Appl.No.: 55,805

[30] Foreign Application Priority Data July 19, 1969 Italy ..52714'A/69 Jan. 14, 1970 Italy..... ..67091 A/70 Feb. 20, 1970 Italy ..67564 N70 [52] U.S. Cl ..417/415, 74/l8.l [51] Int. Cl ..F04b 17/00, F04b 35/04, Fl6j 15/50 [58] Field of Search ..4l7/4l5; 74/18.1

[56] References Cited UNITED STATES PATENTS 1,378,118 5/1921 Jacobsenetal ..74/l8.1

1,687,658 10/1928 Corant ..4l7/238 FOREIGN PATENTS OR APPLICATIONS 584,166 10/1958 Italy ..4l7/4l5 Primary Examiner-Robert M. Walker I Att0rneySughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A compressor for a sealed refrigeration system has a reciprocating piston operated by a drive shaft with an inclined end portion connected to the piston for example via a crank and slotted link. A non-rotatable coupling sleeve is fitted on the inclined end of the drive shaft and sealingly connected to a deformable diaphragm surrounding the shaft and hermetically sealing the bearing for the shaft from the interior of the compressor.

7 Claims, 4 Drawing Figures l COMPRESSORS FOR REFRIGERATION SYSTEMS This invention relates to compressors for refrigeration systems, especially systems of the sealed type.

As is known, compressor refrigeration systems are divided example, a ring of graphite integral with a side wall of the 1 compressor. Such sealing means cannot, however, ensure perfect sealing, and in order to avoid rapid discharge of the refrigerant fluid from the system, there is usually provided, below the condenser, a fluid receptacle adapted to hold a considerable reserve of the said fluid. It is necessary to place in the refrigerant fluid circuit a valve which closes automatically when the system ceases operating, in order to prevent flooding of the evaporator and thereby avoid excessive deliveries of liquid to the compressor upon subsequent starting thereof.

However, with such modulation of the outflow of the refrigerant fluid, a very considerable increase in pressure between the condenser-receiver zone and the zone of the evaporator results during shut-oft" periods, that is, periods when the system is inoperative.

This calls for a considerable static torque for starting the compressor after each shut-off period. For this reason, open systems need three-phase driving motors, or expensive singlephase induction motors with special starting coils, or DC commutator motors with high static torque.

Refrigeration systems of the sealed type on the other hand, can be such that some of the above-mentioned disadvantages of open systems are avoided. Sealed systems are assembled in a single unit, for example in the metal casing either of the mo tor, or of the compressor. In such systems the motor or the compressor is in contact with the stream of refrigerating fluid in circulation.

Sealed systems have the following advantages: they permit perfect sealing; they admit of a limited load of refrigerant fluid; they allow the use of capillary tubes which are less costly than valves required in open systems for achieving the equilibrium of pressures during shut-off periods, and hence they allow start-up under no-load conditions, using motors of low static torque.

On the other hand, the following disadvantages are associated with sealed systems:

a. the motor has to be cooled by the same circulating refrigerant fluid, which lowers the thermodynamic efiiciency of the system;

b. the condenser must be over-sized because it has in addition to dispose of the motor heat;

c. if the condenser is static running, it has to be very large,

unless a forced-ventilation fan is used, which entails an increase in cost;

d. the use of brush motors is not possible, since graphite particles from the brushes would circulate in the refrigerant fluid, and this therefore excludes the whole range of DC refrigeration systems for installation on trains, automobiles, boats and such;

e. sparking of the electric motor leads, after some time, to chemical decomposition of the refrigerant fluid, which results in a change in the operational characteristics of the system.

It is also known from Italian Pat. Nos. 539,581 and 554,535 to provide a refrigerating system with a diaphragm or membrane which defines both an induction and a compression chamber and which at the same time separates the motor space from that of the compressor, thus permitting the use of brush motors and capillary tubes.

In this system, however, one has not eliminated the serious disadvantage in the matter of starting-up under an excessive load. Since the refrigerant fluid has a pressure which is considerably above atmospheric pressure, it is necessary to employ six-pole motors in order to obtain the required static torque.

This invention has the object of eliminating the said disadvantages and achieving some improvements in refrigeration systems of the sealed type, such as to allow the use of the capillary tube, to facilitate no-load starting-up and to permit the use of electric motors of low static torque, including those of the brush type.

Afurther object of the invention is to provide a refrigeration system of the sealed type, in which the motor can be cooled independently of the refrigerant fluid and in which it is possible to reduce the size of the condenser.

Another object of the invention is to provide a refrigeration system of the sealed type, in which the reciprocating compressor canbe operated by an electric motor which is separate from the compressor, or else by an electric motor which is connected to the compressor housing.

In accordance with the present invention there is provided a compressor of the reciprocating piston type for refrigeration systems, especially those of the sealed type, characterised in that the piston is operated by a rotary drive shaft which has an end portion or extension which is inclined to the axis of rotation of the shaft and which is supported by a bearing structure carried by the compressor housing, the inclined end portion or extension of the shaft being connected to the piston by transmission means adapted to convert the rotation of the said shaft end portion or extension into a rectilineal reciprocating movement of the piston, a non-rotatable coupling being engaged upon the inclined shaft portion or extension said coupling having a flange to which an elastically deformable diaphragm is sealingly secured, which diaphragm surrounds the shaft and hermetically seals the interior space of the compressor housing from the support bearing for the drive shaft.

The drive shaft may project, at its end remote from the inclined end portion or extension, from the compressor housing to constitute a drive member which allows its being connected to an independent motor, or else it may form an integral part of the rotor of an electric motor, secured directly to the compressor housing.

Further characteristic features and advantages of the invention will emerge in the course of the following detailed description, given by way of non-limiting example, with reference to the attached drawings, in which:

FIG. 1 is a diagrammatic side view in elevation of a compressor for refrigeration systems according to the invention, directly coupled to an electric drive motor;

FIG. 2 is an axial section on an enlarged scale of the com pressor of FIG. 1 and an end portion of the motor;

FIG. 3, similar to FIG. 2, shows a compressor according to an alternative embodiment, adapted to be driven by a separate motor, and

FIG. 4 is an axial section of a compressor according to a further variant of FIGS. 2 and 3.

Referring to FIGS. 1 and 2, there is shown the outer casing l of an electric motor which in this example is of the DC type having brushes and a rotary shaft 2. The shaft 2 has an outer portion upon which a cooling fan having a bladed rotor 3 is keyed, and an inner portion 2a inclined with respect to the axis of rotation of the shaft 2.

The motor casing 1 is closed at its inner end by a head 4, which supports the said shaft 2 and which has a tubular extension 5 surrounding the shaft 2 and adapted to be joined to the housing 6 of a reciprocating compressor which, in the example illustrated, is of the single cylinder type.

The compressor housing 6 is closed at its upper end by a cap 7 incorporating an induction manifold 8, connected to an induction pipe 8a, and a delivery manifold 9, coaxial with the induction manifold 8 and connected to a delivery pipe 9a.

The induction pipe 8a is connected with the interior space B of the compressor housing 6 by means of a passage 23, shown in broken outline in FIG. 2.

The two manifolds 8 and 9 communicate, by means of induction and discharge valves 10 and 11 respectively, with the interior of a cylinder 12 formed within a sleeve 13 which is fitted in the cap 7. A piston 14 is mounted for fluid-tight sliding movement within the sleeve 13, sealing being provided by a resilient O-ring 15.

Integral with the aforesaid piston 14 there is a lower structure 16 within which a shaped cavity 17 is formed. The cavity 17 is in the form of a slot extending transversely to the axis of the piston 14 and having a part-cylindrical surface with which a cylindrical member 18 mates and is arranged for rocking and axial sliding movement. The cylindrical member 18 is itself traversed by a lateral slot in which the inclined inner end portion 2a of the drive shaft 2 is housed.

The inclined portion 2a of the motor shaft 2 describes a cone upon rotation of the shaft 2. The inclined portion 2a engages the cylindrical member 18 through the interposition of a liner 19 which permits relative rotation of the shaft portion 2a and the cylindrical member 18 in a non-rotating tubular coupling 18a in the form of a sheath with a closed end through the interposition of a liner 19 which permits relative rotation of the shaft portion 2a and the coupling 18a, the latter being secured within the lateral slot in the cylindrical member 18 so as to follow the revolutions of the shaft 2 without moving angularly around its own axis. The members 2a, 18a, 18 and 16 form in effect a crank and slotted link mechanism which transforms the rotational movement of the inclined portion 2a of the shaft into a rectilineal reciprocating motion of the piston 14.

The tubular coupling 18a is provided at one end with a plane flange 20, to which an elastically deformable diaphragm 22 is connected and sealed by means of a cooperating annular clamping plate 21. The diaphragm 22, which surrounds the end of the shaft 2, is clamped at its outer periphery between the housing 6 of the compressor and the tubular extension which is integral with the head of the motor.

The diaphragm 22 therefore seals off at the end of the motor casing 1 a space A, constituting for example a reservoir for lubricating oil, which is separated hermetically from a space E within the compressor housing 6. Either the lubricating oil or the refrigerant fluid of the system may be circulated in the space B. As is seen in the drawings, the diaphragm 22 comprises an annulus of uniform thickness so that in its undeformed state it is flat, being made from sheet material.

By this means the only sealed part of the motor-compressor unit is the compressor, and the motor can if desired be positioned outside the sealed part.

The above described motor-compressor unit can be employed in a refrigerating system which includes capillary tubes, on account of the fact that the compressor is sealed.

Moreover the unit can start-up at no-load, with low static torque, since the difference in pressure between the refrigerant fluid and the atmosphere has no effect whatever upon the static torque. This unit therefore also permits of the use of relatively economical two-pole DC motors of the brush t pe.

The motor being of the open (non-sealed) type, is not frozen by the refrigerant fluid. Moreover the motor may have upon the front end of its shaft, as shown in FIG. 1, a fan which allows the use of a condenser having forced ventilation, which is very small and economical compared with condensers relying upon natural convection. Moreover the condenser does not have to dispose of the heat generated by the motor, as is usually the case in sealed systems, so that the thermodynamic efiiciency of the whole system is improved.

In FIG. 3 there is illustrated a compressor the piston of which is driven by the inclined end portion 2a of a motordriven shaft 2. The shaft 2' is supported by a bearing structure 40, provided with an external flange 41 by which it is connected to the compressor housing 6.

Separation of the space B within the compressor housing 6 and the closed space A within the bearing structure 40, is effected by the elastic diaphragm 22 which is clamped at its outer periphery between the flange 41 of the structure 40 and a corresponding face of the compressor housing 6.

The bearing structure 40 is provided internally with a central tubular support 42, in which the drive shaft 2' is supported for rotation in an oil bath in the space A.

The shaft 2 projects, at one of its ends 2'b, externally of the bearing structure 40 and it has, keyed on to this projecting end 2'b an externally grooved pulley 43 or a similar dn've member, adapted to be drivingly connected to an electric motor (not shown) which is independent of the compressor, by way of a flexible endless belt or wire rope.

The transmission of drive from the motor to the compressor may, of course, be effected by other means, for example by chains, gears or elastic couplings.

The elastic diaphragm 22 makes it possible to seal off the compressor space B from the space A, which is oil-filled.

The embodiments described can be used advantageously in high-power systems in which separate motors can be used; compared with the usual open compressors these embodiments have the advantage of being able to use the capillary tube instead of the restrictor valve, thus eliminating the need for a liquid receptacle.

Moreover it is possible to use motors of very low static torque, single-phase or three-phase motors, and AC or DC motors.

In FIG. 4 there is illustrated a compressor according to the invention, in which the kinematic connection between the piston 14 and the inclined end portion of the drive shaft is formed by a connecting rod and a spring.

The drive shaft 2, which may be integral with an electric motor or can be independent of it, has a straight end portion 2'a, projecting into the space B of the compressor housing 6. In this end portion there is formed blind bore 24 the axis x x of which is inclined to the axis of rotation of the shaft 2.

An extension shaft or pin 25 is located in the bore 24 and projects beyond the end of the shaft 2, inclined at an angle to the axis of the shaft 2. Two roller bearings 26 are rotatably supported on the extension shaft 25 and in turn support a tubular coupling or shaft 27, closed at one end, which partly surrounds the shaft 2. The coupling 27, being inclined to the axis of the shaft 2 describes, as a result of the rotation of the shaft 2 a surface of revolution body which is substantially bi-conical,

without however rotating about its own axis.

The coupling 27 is provided at one end with a flange 20a to which a deformable elastic diaphragm 22 is sealingly connected, the diaphragm 22 being sealingly anchored between the tubular extension 5 and the compressor housing 6.

The piston 14 of the compressor has on its lower portion a tubular skin 32, in which there is made a cavity 31 tapering in cross section towards a spherical bottom. The oscillating coupling 27 has a seating 30 in which a cavity 29 with a similar tapered shape, and a spherical bottom, is formed.

In the cavity 29 of the coupling 27 and the cavity 31 of the piston 14 there are engaged respective rounded opposite ends of a rigid connecting rod 28 which constitutes a kinematic connection between the shaft 2 and the piston 14.

The piston 14 is further connected to the coupling 27 by means of an upwardly tapering helical spring 33, the upper coils 33a of which are seated in a helical groove made in the external surface of the piston skirt 32. The spring 33 has at its lower end a terminal turn 33b which is bent so as to form a half-loop 34 encircling the tubular coupling 27 and which is located between a pair of projections 35 formed on the said coupling 27 diametrically opposite the seating 30.

Since the coupling 27 follows the rotation of the inclined extension shaft 25 the seating 30 will describe a circle in space, the diameter of which circle corresponds to the stroke of the plston.

Hence, with the connecting rod 28 in contact with both the cavity 29 of the seating 30, and the cavity 31 of the piston skirt 32, the tension of the spring 33 is sufficient to avoid, in the induction phase of operation of the pump, any breaking away of the spherical ends of the rod 28 from their respective seating cavities 29, 31, it is clear that the rod 28 will operate like a normal connecting rod assembled upon an eccentric,and will transform the rotational movement of the shaft 2 into a reciprocating movement of the piston M.

The aforesaid connecting rod, even when assuming different positions in order to follow the locus circle described by the coupling 27 in comparison with the linear displacement of the piston, will generate neither substantial friction nor tension, because the spherical ends of the rod 28 fit easily into the two cavities 29, 31, and only the spring 33 will sufier slight distortions of axial ilexure, which are negligible in practice.

Use of the spring 33 in the embodiment of FIG. 4 makes it possible to recover automatically any possible play between the connecting rod 38 and its seatings cavities 29, 31. The conical form of the spring is intended to reduce the distortions of the upper turns, which are nearest to the piston 14. 1

The construction and assembly of the unit according to the invention is simple and will ensure a high mechanical efficiency to the drive. The low power loss makes the use of the unit advantageous in all cases in which very low power losses are required.

I claim: a

1. A sealed compressor of the sliding piston type for refrigerations systems, comprising in combination: '(i) piston mounted for sliding movement in a cylinder; (ii) a rotary drive shaft having an end portion which is inclined at an oblique angle to the axis of rotation of the shaft; (iii) a compressor housing; (iv) bearing means carried by the compressor and supporting said shaft; (v) transmission means connecting the shaft to the piston and converting the rotation of said shaft end portion into a sliding movement of the piston in the cylinder; (vi) a non-rotatable sheath having a closed end and being engaged upon the inclined shaft portions; (vii) a flange on said sheath; and (viii) an elastically deformable diaphragm in the form of an annulus sealingly secured at its radially inner edge to said flange on said sheath and at its radially outer edge to the compressor housing, said diaphragm surrounding the shaft and in combination with said sheath sealing the interior of the clompressor housing from the support bearing for the drive s aft.

2. A sealed compressor according to claim I, in which the transmission means connecting the piston to the drive shaft comprise a rigid connecting rod having rounded ends, a seating cavity formed in the bottom of the piston, one end of said connecting rod being seated therein, and a similar cavity formed in the non-rotatable sheath in which the other end of the connecting rod seats, and a spring coaxially surrounding said connecting rod and secured at opposite ends to the piston and to the sheath.

3. Compressor according to claim 2, in which the end turn of the spring nearest the sheath is bent into a half-loop and two projections are provided on the sheath opposite the respective seating cavity with which the rigid connecting rod engages, the said half-loop of the spring being located between said projections.

41. Compressor according to claim 2 in which the piston has a skirt surrounding the respective seating cavity for the rigid connecting rod, the turns of the spring nearest the piston being threaded on to said skirt.

5. Compressor according to claim 2, in which the spring has a conical shape, flared out towards the end connected to the coupling, in order to reduce the distortion of the turns closest to the piston.

6. A compressor according to claim 1, in which the diaphragm is formed from sheet material, said sheet material being flat in its undefonned state.

7. A compressor according to claim 1, wherein the inclined end portion of the drive shaft comprises a pin fixed in a bore in the shaft and inclined to the shaft axis. 

1. A sealed compressor of the sliding piston type for refrigerations systems, comprising in combination: (i) piston mounted for sliding movement in a cylinder; (ii) a rotary drive shaft having an end portion which is inclined at an oblique angle to the axis of rotation of the shaft; (iii) a compressor housing; (iv) bearing means carried by the compressor and supporting said shaft; (v) transmission means connecting the shaft to the piston and converting the rotation of said shaft end portion into a sliding movement of the piston in the cylinder; (vi) a nonrotatable sheath having a closed end and being engaged upon the inclined shaft portions; (vii) a flange on said sheath; and (viii) an elastically deformable diaphragm in the form of an annulus sealingly secured at its radially inner edge to said flange on said sheath and at its radially outer edge to the compressor housing, said diaphragm surrounding the shaft and in combination with said sheath sealing the interior of the compressor housing from the support bearing for the drive shaft.
 2. A sealed compressor according to claim 1, in which the transmission means connecting the piston to the drive shaft comprise a rigid conneCting rod having rounded ends, a seating cavity formed in the bottom of the piston, one end of said connecting rod being seated therein, and a similar cavity formed in the non-rotatable sheath in which the other end of the connecting rod seats, and a spring coaxially surrounding said connecting rod and secured at opposite ends to thepiston and to the sheath.
 3. Compressor according to claim 2, in which the end turn of the spring nearest the sheath is bent into a half-loop and two projections are provided on the sheath opposite the respective seating cavity with which the rigid connecting rod engages, the said half-loop of the spring being located between said projections.
 4. Compressor according to claim 2 in which the piston has a skirt surrounding the respective seating cavity for the rigid connecting rod, the turns of the spring nearest the piston being threaded on to said skirt.
 5. Compressor according to claim 2, in which the spring has a conical shape, flared out towards the end connected to the coupling, in order to reduce the distortion of the turns closest to the piston.
 6. A compressor according to claim 1, in which the diaphragm is formed from sheet material, said sheet material being flat in its undeformed state.
 7. A compressor according to claim 1, wherein the inclined end portion of the drive shaft comprises a pin fixed in a bore in the shaft and inclined to the shaft axis. 